X p process of haking soditfm solpbide



Mar. 6, 1923.

F, G. STANTIAL ET AL.

PROCESS 0F MAKING SODIUM SULPHIDE Filed July l0, 1922 t.; itil if. .lai..

l rare orifice.

rnann e. srnn'rian or MELROSE, Ann Jenin n. enanas, os* wlncnss'rnit,MASSA.

cnusnrrs, Assionons fro iunnnnvrac enmarcar. continuit, on wonnen',MASSA- cuusn'rrs, n' eonronarron ort'i'nsssonosnr'rs.

rnoonss or tannins sanitaria.'surniinnY application ,sied :my vsie',

To all 'who-m t may concern: y. Be it lnown that we, (l) yFRANK brani''rIAL and (2) donn ld. llnaniin, citizen of)k l) the United States, (2).Canada,subgectprl the King ofGreat. Britain, residing (if 14:6 FlorenceStreet, Melrose, (2) 2731Main,

"Street, Winchester, in the county of (l)l ll/liddleserr7 Middlesex,andState Qf"( l)' Massachusetts, (2) `lidassachusetts,y have inventedcertain new and useful Improvementsl in Processesfof Making SodiumrSulphide, of which the following is a speciication.

This invention relates to the process for the manufacture of sodiumsulphide in which sodium sulfate isreduced tothe s.ul--l plaide by meansofya carbonaceous reducing agent. i

The usual method of making sodium lsulphide comprises heating a mixtureof sodium sulfatey or sodium acid sulfate 'andcarbof naceous material,such as coal or coke, on the bed of a reverbera'toryfurnaceto atemperature of about 1000G C. in a reducing` atmosphere produced byburning softcoal, oil, gas or other fuel. ln this'process the charge ismelted or reduced to a semifused mass in order to secure intimatecontactbetween the sulfate and the reducing agent and further tofacilitate the rabbling and mixing 0f the charge. In order to maintainthe charge in a fused or plastic condition a temperature considerablyabove the mini-y mum temperature necessary for reaction be-y tween tliesulfate and the carbonaceous ina-l terial must be maintained andthisresults in loss of heat, loss of material byvvolatilization and theformation of undesirable impurities. The fused charge acts destructivelyupon the furnace linings which lnot only gives rise to heavy maintenanceycosts but also introduces impurities -into theffur-` nace product. f

Moreover, for rabbling they charge, hand labor of a very exacting natureis required.

In another pro-cess of making.` sodium sulphide some'of the mentioned,objectionable features of the usual process are obviated by avoidingfusion of the' charge. rlhis process, however, involves a very finegrindf ing or pulverizing of both the sodium sulfate and thecarbonaceous material.

An object of our invention Iis to avoid the tine grinding or pulverizingof the Vmaterials and also to avoid the various disadvantages ieee'..serial No. 573,311.V

incident to the use of high temperatures and mass fusion of the charge.i Y. A further object of our invention is the completeutilization of thematerials entering into the reaction, thatis, the sodium sul-r fromunreduced sulfate and uneonsumed carbonaceous material, and returningthe re'- covei'ed sulfate and carbonaceous material to the proeess, e ii 'l il Y' I j ln thev following detailed description of the inventionreference is made to the accompanying drawing in which the figure is ahorizontal view partly in section of one form of apparatus suitablefor'carrying out the process.

Referring to the drawing, l is a Iconveyor; adapted to receive rawcrushed niter cake or ground saltcake and coke from a suitable source ofsupply and also recovered coke and sodium sulfate together with otherrecovered sodium lsalts from the revolving dryer 3 and to deliver thematerial to the revolving preheater and decompose-r 2. From therevolving preheater and decoinposer Q the material is delivered to theArevolving reducing furnaceA: by way of the conveyor 6. f

From the reducing 'furnace 4 the reaction product, consistingprincipally of unconsumed coke, sodium sulfate and sodium sulphide,passes to apparatus for recovering these materials, the4 coke andsulfate and otherrecoverjed sodium salts beingreturned to theprocesswith fresh materials and the sodium sulphide being withdrawn as afinal product. The furnace product contains sodium salts other thansodium sulfate and sodium sulphide which are separated from thesodiumsulphide along with the sodium sulfate and coke and returned to theprocess.

ln the following description and claims reference will be made to thethree principal constituents of the furnace product only, that is, theunconsumed coke, the uncoiiverted sodium sulfate and the sodium sul.

f phide, it being understood that the other sodium salts present areseparated, recovered and returned to the process along with therecovered coke and sodium sulfate. The disl v.-lv l l sepaiatnig theresulting sodium` sulphidev` Cil solving and recovery apparatus isillustrated in the drawing more or less diagrammatically. As illustratedthe furnace et discharges into the dissolving tanlr 9 in which thematerial is agitated with water or washings in quantity sufficient orless than sui'licient to dissolve the sodium sulphide content. Theproduct of the operation carried out in tank 9 consisting principally ofcoke, undissolved sodium sulfate with possibly small amounts ofundissolved sodium sulphide and a solution of sodium sulphide passes toapparatus for separating coke and sodium sulfate from the sodiumsulphide solution. Any suitable form of leaching and displacementapparatus may be used for this purpose but we preferably employ a systemsuch as that illustrated in the drawings. The mixture of coke,undissolved sodium sulfate, and sodium sulphide solution passes fromtank 9 to the coarse coke trap 10` in which the coarse coke and the bulkof the sodium sulfate are settled andwashed by means of a countercurrent of water or washings from the centrifugal 11 as indicated, thesodium sulphide solution with some fine coke and sodium sulfate passingto the settler 13 in which substantially complete separation of the cokeand undissolved sodium sulfate from the sodium sulphide solution isaccomplished, the settled material being washing by a counter currentflow of water or washings from the centrifugal 11 as indicated. Theclear sodium sulphide solution formed in the settler 13 is withdrawn forthe recovery of sodium sulphide by crystallization or is conveyed to theconcentrating pans 8 or both as indicated. rllhe coarse coke and sodiumsulfate separatedl in the coarse coke trap 10 and the fine coke andsulfate separated in the settler 13 are discharged into the centrifugal11 where they are washed with water, the wash water supplying the coarsecoke trap 10 and the settler 13 as indicated. The washing of therecovered coke and sulfate preferably is accomplished by charging thecentrifugal 11 periodically with coarse coke and sulfate from the trap10 and then with fine coke and sulfate from the settler 13. By operatingin this manner the coarse coke and sulfate forms a bed or a sort of sandfilter upon which the fine coke and sulfate is deposited and held whileit is being washed. The Washed coke and sulfate is delivered from thecentrifugal 11 through the conveyor 12 to the revolving dryer 3.

In the above described operation for the recovery of sodium sulphidesolutions of maximum concentration are employed in order to secure amore or less complete sepa-` ration of the sodium sulphide in solutionfrom sodium sulfate in the undissolved residue.

The centrifugal 11 may be replaced by equivalent apparatus such as asuction filter.

In practice the apparatus represented by the coke trap 10 and thesettler 18 preferably is some approved form of classifiers or series ofclassifiers and settlers designed for the ,washing7 displacement andseparation of solid materials from soluble constituents.

Further details of the apparatus will appear in the followingdescription of the operation of the process.

Carbonaceous material in granular form, preferably a material low in ashcontent such as petroleum coke and sodium acid sulfate preferably in theform of crushed or coarsely ground niter cake are fed into the conveyer1 in the proportions of about 1 part of niter cake to 1.5 more or lessparts of colte. The proportions of coke and niter calze will varyconsiderably depending upon vthe condition of the process and therelative proportions of recovered coke and sodium sulfate being suppliedto the conveyor 1 from the dryer 3. The coke and niter calze aresupplied in suffiu cient proportion to maintain in the process asubstantial excess of coke over that required for the reduction, thebull: of the colre in the charge being in granular form, say about #8mesh as distinguished from powdered material.

The charge of coke and niter cake with recovered coke and sulfate isdelivered by the conveyor 1 to the revolving preheater and decomposer 2which is maintained at about 4000 C. by waste heat from the furnace fl.,ln the preheater 2 the niter cake fuses and due to the mixing andtumbling of the charge forms a coating or film upon the coke. Noreduction of sulfate to sulphide occurs in the decomposer 2 at theteinperature employed Abut the free acid of the niter cake reacts withthe coke :forming sulfur dioxid and oxides of carbon. rlhe gas evolvedfrom the decomposer contains high as from A to 65 per cent of sulfurdioXid and may be used in various ways.

The coke, coated with sodium sulfate resulting from the treatment in thedecomposer 2 and preheated to the extent of about 40 per cent passes byway of conveyor 6 into the revolving reducing furnace 4 which ismaintained at a temperature sufficientto accomplish reduction of thebull; of the sulfate. A temperature between 8000 C. and 100()o C. issuitable for this purpose the lower temperature being preferred. Thefurnace 4 is heated in any suitable manner such as by a reducing flameproduced by burning oil with air as indicated.

The gases leaving the furnace 4 are at a high temperature and moreovercontain a considerable amount of carbonio oxid. This gas is supplied tothe furnace chamber 7 where it is mixed with sufficient air to sup'-port complete combustion and the resulting hot gases and products ofcombustion then pass under the concentrating pans 8, the deapparatus bythe waste gases from furnace e is insufficient. A s

The material discharged from the furnace 4: is treated for the recoverycf sodium sull phide and unreduced sodium. sulfate and un-` consumedcoke as described above, the recovered coke and sulfate being deliveredto passes in va dry.,

the dryer 3 from which .itl condition to the conveyor l. i Y

The apparatus is illustrated and described as being arrangedhorizontally, conveyors being` employed for progressing the solidmaterials throughy the apparatus. It is to be understood however, thatthe invention is not limited in this respect since it will be apparentthat the apparatus may be arranged vertically, the solid materials passing through the apparatus by gravity, and the conveyors may be omitted.y

ln the above described process in ywhich sodium acid sulfate (nitercake) is em ployed, after the free acid of the niter cake has beendecomposed with the production of a gaseous product rich in sulfurdioxid, the sodium sulfate in contact with the coke in the form of thinfilms is quickly and efficiently reduced to the sulphide at a rela--ytively low temperature without mass fusion. Loss by volatilization, theformation of byproducts by longr heating andthe action of the charge onthe furnace linings are thus largely avoided. Since the charge passesthrough the furnace in a granular condition hand rabbling isunnecessary. The process is largely automatic and rapid, resulting in anexcellent yield and relative-ly large out put. Moreover the process iseconomical in which comprises, mixing niter cake and coke,

the use of fuel and materials and the expense for apparatus 11p-keep andlabor is small. n

ln the process described above using niter cake as the starting materialthe niter cake is fused at the relatively low temperature employed inthe decompose'rQ and coats theA coke granules, the niter cake coatingbeing converted to sodium sulfate by decomposr tion of its free acidcontent. Small amounts of this sodium sulfate become detached from thecoke particles as the `charge progresses through the decomposer 2 andthe furnace but it is found that thistletached material is picked up bythe tumbling coke granules and reduced. lt is further noted that therecovered sulfate coming from the dryer is in the form of sodium sulfateand is not fusible at the temperature employed in the decomposer 2 but.this sodium sulfate is picked upy and held by t-he coated coke granulesand is efficiently reduced. A comparatively large proportion of sodiumsul fate may be used in thecharge along with the niter cake, the sodiumsulfate or salt' cake preferably being in fairly finely divided orpowdered condition. The process may even be operatedwith .salt cakealone, that is, by feeding into the conveyor l a mixture of granularcoke and powdered cake. y The salt cake does not fuse and coat thegranular coke with a film of sodium sulfate as whenniter cake isemployed. i However when saltfcake is used alone the process yproceedsin a satisfactory manner and under rsubstantially the same conditions ass e i' in .i seonieca. ue

thoereiired theu fit1 le D to the continuous tumbling of the charge intherevolvin'g decomposer EZand the furnace i the saltcake is picked upby and adheres to the coke granules and is reduced and during thepassage of the charge through the reducing'furnace it is found thatsubstantially all of the salt has thus been picked up Vand reduced. Theronly differences inthe process when salt cake or a predominatingproportion of salt cake kis used instead of niter cake are that the saltcake must be powdered whereas the niter cake need not be powdered andthat no sulfur dioxid con- )taining gas is produced in the decomposer 2yfrom salt cake whereas gas rich in sulfur dioxid is produced indecomposer 2 by the decomposition of the niter cake.

We claim:

1. Process of making sodium sulphide which comprises, reducing sodiumsulfate in the form of a molten non-flowing lm in contact withcarbonaceous material.

s p 2. Process of making sodium sulphide which comprises, coatinggranules of carbonaceous material with a relatively thin layer of sodiumsulfate, and heating and agitating the coated granules.

r3. Process of making sodium sulphide .ular carbonaceous material andsodium sul- Vfate to temperature sufficient to reduce the sodium sulfateto sulphide, selectively dissolving sodium sulphide from the reactionproduct, and returning unconsumed carbonaceous materialand unreducedsodium sulfate and other sodium salts to the heat ing operation. y

6. Process of making sodium sulphide whichy comprises, heating vandagitating a mixture of sodium sulfate and granular coke to a temperatureof from 800O C. to 10000 C., leaching the heated material with water,separatinf the resulting sodium sulphide solution irom coke andunreduced sulfate and other sodium salts, drying the coke and sulfateand other sodium salts, and returning the saine to the heatingoperation.

7. Process oi? making sodium sulphide which comprises, agitating amixture of niter cake and granular petroleum colte While heatingl themixture to about 400o C. until the granules of coke are coated withsodium sulfate, and continuing the agitation of the mixture at atemperature of 800O C. to 10000 C. until the hulk of the sodium sulfateis reduced to sodium sulphide.

8. Process of making sodium sulphide which comprises, mixing niter cakeWith granular earbonaceous material in excess of the quantity suiiicientto reduce the sulfate to sulphide, heating and agitating the mixu tureat a temperature suiicient to cause the coating of the carhonaceousgranules with sodium sulfatebut insuiicient to cause suhstantialreduction of the sulfate to sulphide,

continuing` the agitation of the mixture at.

a temperature suicient to cause reduction of the sulfate, leaching thereaction product With Water, sepafatingA the resulting solution oi'sodium sulphide from sodium sulfate and other sodium salts andcarbonaceous material, dryingthe sodium sulfate and other sodium saltsand carbo-naceous material, and returning the same to the rst named heatinfr'and agitating operation.

4n testimonf,7 whereof, we aiix our signatures.

FRANK G. STANTIAL. JUHN H. CLARKE.

